Astronomers Detect Unprecedented 24-Hour Gamma-Ray Burst

On July 2, 2025, astronomers observed a gamma-ray burst (GRB) that defies conventional understanding due to its unprecedented 24-hour duration. Designated GRB 250702B, this event was first detected by NASA's Fermi Gamma-ray Space Telescope, which recorded three bursts from the same source over several hours. Subsequent data from the Einstein Probe revealed that the source had been active nearly a full day earlier.

Typically, GRBs last from milliseconds to several minutes and are associated with the collapse of massive stars or the merging of neutron stars. The prolonged and repetitive nature of GRB 250702B challenges these models. Antonio Martin-Carrillo, co-lead author of a study on the discovery, stated, "This GRB is different from any other seen in 50 years of observations."

Follow-up observations using the Very Large Telescope and the Hubble Space Telescope identified the burst's origin in a distant galaxy, several billion light-years away. This extragalactic source suggests that the event was significantly more powerful than initially estimated. Andrew Levan, co-lead author and astronomer at Radboud University, noted, "If this is a massive star, it is a collapse unlike anything we have ever witnessed before."

One hypothesis proposes that the burst resulted from a white dwarf being disrupted by an intermediate-mass black hole, a scenario that remains poorly understood. Martin-Carrillo emphasized the need for further research, stating, "We are still not sure what produced this, but with this research, we have made a huge step forward towards understanding this extremely unusual and exciting object."